.\"-
.\" Copyright (c) 2023 Dag-Erling Smørgrav
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd September 5, 2023
.Dt STDCKDINT 3
.Os
.Sh NAME
.Nm stdckdint
.Nd checked integer arithmetic
.Sh SYNOPSIS
.In stdckdint.h
.Ft bool
.Fn ckd_add "type1 *result" "type2 a" "type3 b"
.Ft bool
.Fn ckd_sub "type1 *result" "type2 a" "type3 b"
.Ft bool
.Fn ckd_mul "type1 *result" "type2 a" "type3 b"
.Sh DESCRIPTION
The function-like macros
.Nm ckd_add ,
.Nm ckd_sub ,
and
.Nm ckd_mul
perform checked integer addition, subtraction, and multiplication,
respectively.
If the result of adding, subtracting, or multiplying
.Fa a
and
.Fa b
as if their respective types had infinite range fits in
.Ft type1 ,
it is stored in the location pointed to by
.Fa result
and the macro evaluates to
.Dv false .
Otherwise, the macro evaluates to
.Dv true
and the contents of the location pointed to by
.Fa result
is the result of the operation wrapped to the range of
.Ft type1 .
.Sh RETURN VALUES
The
.Nm ckd_add ,
.Nm ckd_sub ,
and
.Nm ckd_mul
macros evaluate to
.Dv true
if the requested operation overflowed the result type and
.Dv false
otherwise.
.Sh EXAMPLES
.Bd -literal -offset indent
#include <assert.h>
#include <limits.h>
#include <stdckdint.h>

int main(void)
{
	int result;

	assert(!ckd_add(&result, INT_MAX, 0));
	assert(result == INT_MAX);
	assert(ckd_add(&result, INT_MAX, 1));
	assert(result == INT_MIN);

	assert(!ckd_sub(&result, INT_MIN, 0));
	assert(result == INT_MIN);
	assert(ckd_sub(&result, INT_MIN, 1));
	assert(result == INT_MAX);

	assert(!ckd_mul(&result, INT_MAX / 2, 2));
	assert(result == INT_MAX - 1);
	assert(ckd_mul(&result, INT_MAX / 2 + 1, 2));
	assert(result == INT_MIN);

	return 0;
}
.Ed
.\" .Sh STANDARDS
.\" The
.\" .Nm ckd_add ,
.\" .Nm ckd_sub ,
.\" and
.\" .Nm ckd_mul
.\" macros conform to
.\" .St -isoC-23 .
.Sh HISTORY
The
.Nm ckd_add ,
.Nm ckd_sub ,
and
.Nm ckd_mul
macros were first introduced in
.Fx 14.0 .
.Sh AUTHORS
The
.Nm ckd_add ,
.Nm ckd_sub ,
and
.Nm ckd_mul
macros and this manual page were written by
.An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .
